Engines, including diesel engines, gasoline engines, gaseous fuel powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants include solid material known as particulate matter or soot. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of particulate matter emitted from an engine is regulated depending on the type of engine, size of engine, and/or class of engine.
One method implemented by engine manufacturers to comply with the regulation of particulate matter exhausted to the environment has been to remove the particulate matter from the exhaust flow of an engine with a device called a particulate trap. A particulate trap is a filter designed to trap particulate matter and typically consists of a wire mesh or ceramic honeycomb medium. Although the particulate trap adequately removes particulate matter from the exhaust flow of an engine, the use of the particulate trap for extended periods may cause excessive amounts of the particulate matter to build up in the medium. This buildup may reduce the functionality of the filter and subsequent engine performance.
The collected particulate matter may be removed from the filter through a process called regeneration. To initiate regeneration of the filter, the temperature of the particulate matter entrained within the filter must be elevated to a combustion threshold, at which the particulate matter is burned away. One way to elevate the temperature of the particulate matter is to inject fuel into the exhaust flow of the engine and ignite the injected fuel. Electrical devices such as a thermocouple, an igniter, a pressure sensor, or any other electrical device known in the art, may be employed to facilitate or provide feedback for the regeneration process.
After the regeneration event, the supply of fuel is shut off. However, during regeneration some fuel may spray and remain on the electrical device. This remaining fuel, when subjected to the harsh conditions of the exhaust stream may coke or be partially burned, leaving behind a solid residue that can foul the electrical devices. This fouling can cause the electrical device to send poor readings or, in the case of an igniter (e.g. a spark plug), to ground out. In addition, particulate matter and/or other debris may enter a cavity housing the electrical device from the exhaust flow, and similarly foul the electrical device. For this reason it may be necessary to periodically purge the electrical devices and the cavities in which they are housed.
One method of purging an electrical device is described in U.S. Pat. No. 6,003,487 (the '487 patent) issued to Merritt on Dec. 21, 1999. Specifically, the '487 patent discloses a spark plug housed in a cavity of a combustion engine's cylinder. The cavity is purged by “toroidal” movement of air and fuel. That is, two cylinders connected by an orifice share the same combustion space when their respective pistons are at the inner dead center positions. As the pistons reciprocate they generate the “toroidal” flow within the combustion space to provide better mixing of air with an injected fuel. The spark plug cavity is in communication with one of the two cylinders and is purged with this “toroidal” air-fuel mixture. Because the cavity is open to the common combustion space at a spark end, the “toroidal” flow of fuel-air mixture passes into the cavity and around the spark end, thus purging the spark plug.
Although the spark plug may benefit somewhat from the purging process described in the '487 patent, the effectiveness of the purging may be limited. Specifically, because the spark plug of the '487 patent is purged with a fuel-air mixture, some residual fuel may remain on the spark plug or within its cavity, even after the purging process is complete. This residual fuel, under the heat of combustion, may still coke and cause fouling. In addition, the design of the '487 patent may have limited functionality in an exhaust regeneration device that does not have any pistons to generate a specific air flow pattern.
The regeneration device of the present disclosure solves one or more of the problems set forth above.